Electrodeposition of nickel on uranium



ELECTRODEPOSITION OF NICKEL N URANIUM Allen G. Gray, Rocky River, Ohio,assignor to the United States of America as represented by the UnitedStates Atomic Energy Commission No Drawing. Application January 9, 1945Serial No. 572,092

3 Claims. (Cl. 204-15) This invention relates to the preparation ofmetallic surfaces for the application of coatings. It is particularlyconcerned with the preparation of metals above iron I in theelectromotive series for the application of adherent electro-deposits.

The preparation of metals high in the electromotive series for coatingis rendered diflicult by the strong tendency of such metals to formcompounds with any reagent with which the metals are contacted. Thusthey react readily with the oxygen in air to form metal oxide filmswhich coat the metal surface and prevent adherence of electrodeposits tothe metal. Similar films are formed by contact of the metals withaqueous solutions.

It is an object of the present invention to prepare such metals so thatcoatings subsequently applied can adhere firmly to the metal surface. Afurther object of the invention is the treatment of such metals toprovide protection for the surfaces so that they will not be attacked byaqueous electroplating solutions. Still further objects will be evidentin the light of the following description of the invention.

In accordance with my invention a metal above iron in the electromotiveseries is treated with a molten hydrate of ferric chloride, particularlyFeCl .6H 0 at a temperature above 37 C. (its melting point). Thistreatment etches the metal surface, providing a structure most suitablefor the application of adherent electro-deposits and at the same timeplates the surface electromotively with metallic iron. The metallic ironadheres firmly to the base metal, and though an extremely thin film,retards the action of aqueous electroplating solutions and avoids theformation of interfering non-metallic films on the metal surface beforethe coating metal to be electroplated begins to deposit.

, The process of the invention is applicable to metals above iron in theelectromotive series, such as uranium, aluminum, magnesium, and zinc.

Preferably the preparatory treatment is effected with molten FeCl .6H Oat a temperature between 50 C. and 70 C. for between about 1 minute andabout 3 minutes. In treating large batches of metal an initial bathtemperature of about 70 C. can be used to advantage to warm the metal tothe treatment temperature while the bath temperature is allowed to fallto 50-60 C.

'Before the metal is subjected to the etchant treatment with ferricchloride, it may be cleaned to remove foreign matter and metal oxides.Such cleaning may comprise washing with a grease solvent or with adetergent solution, sand-blasting, scrubbing with pumice, or dissolvingoxide film with a reagent such as concentrated nitric acid.

Patented Aug. 26, 19.58

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After the etchant treatment it is desirable to electroplate the metalsurface promptly while it still retains the character of a freshlyprepared electromotive coating. The metal thus may be plated inconventional electroplating solutions such as acidic nickel, iron, andchromium, and acidic or basic copper and zinc electroplating baths.

The following examples illustrate the inventioni Example 1 A metallicuranium rod is dipped for about 30 seconds in aqueous 50% (by Weight)I-INO solution at about 20 C. The article is then rinsed in water,dried, and dipped in molten ferric chloride hexahydrate (FeCl .6H O)maintained at about 50 C. until the rod is coated with an adherent blackfilm of metallic iron. This requires about 30 seconds. The rod is thenthoroughly rinsed in water and immersed in a nickel electroplating bathcontaining, per liter of solution, 240 grams of NiSO .7H O, 45 grams ofNiCl .6H O and 30 grams of H BO With the rod as cathode a current ispassed through the solution at a cathodic current density of 25 amperesper square foot. In fifteen minutes the rod is plated with a firmlyadherent nickel electroplating about 0.0003 inch thick.

Example 2 A small aluminum strip is dipped in molten ferric chloridehexahydrate (FeCl .6H O) at 50 C. until it is coated with a blackadherent film of metallic iron (about 1 minute). The coated metal iswashed with water and electroplated as in the preceding example. Anunusually adherent nickel electroplating is thus formed on the aluminumsurface.

It will be understood that I intend to include variations andmodifications of the invention and that the preceding examples areillustrations only and in no wise to be construed as limitations uponthe invention, the scope of which is defined in the appended claims,wherein I claim:

1. A process for preparing metallic uranium for the application of anadherent electro-deposit upon its surface which comprises treating saidsurfacewith molten ferric chloride hexahydrate.

2. A process as defined in claim 1 wherein the treatment is carried outat a temperature between 50 C. and C.

3. In the application of a nickel electroplating to metallic uranium,the improvement which comprises treating the surface of the uranium withmolten ferric chloride hexahydrate between 50 C. and 70 C. until a blackfilm covers the metal surface, washing the surface with water andpromptly electroplating it in an aqueous nickel sulfate electroplatingbath.

References Cited in the file of this patent UNITED STATES PATENTS2,162,789 Raub June 20, 1939 FOREIGN PATENTS 446,949 France Dec. 18,1912 476,720 Great Britain Dec. 14, 1937

3. IN THE APPLICATION OF A NICKEL ELECTROPLATING TO METALLIC URANIUM,THE IMPROVEMENT WHICH COMPRISES TREATING THE SURFACE OF THE URANIUM WITHMOLTEN FERRIC CHLORIDE HEXAHYDRATE BETWEEN 50*C. AND 70*C. UNTIL A BLACKFILM COVERS THE METAL SURFACE, WASHING THE SURFACE WITH WATER ANDPROMPTLY ELECTROPLATING IT IN AN AQUEOUS NICKEL SULFATE ELECTROPLATINGBATH.